1. Field of the Invention
The present invention concerns an optical device suitable, for example, to display apparatus for conducting display of numericals or characters or X-Y matrix display, as well as an optical filter capable of controlling light transmissivity or light reflectivity in a visible light region (wavelength at 400 to 700 nm), as well as a fabrication method thereof and a driving method thereof.
2. Description of the Related Art
An electrochromic display device (hereinafter simply referred to as xe2x80x9cECDxe2x80x9d) employed so far in display apparatus such as digital watches is a non-light emission type display device which conducts display by reflection light or transmission light as a light control device by electrochemical operation, so that it has a merit giving less feeling of fatigue even in long time observation, as well as a merit that it requires relatively low driving voltage and less consumption power.
For instance, as disclosed in Japanese Published Patent Application No. Sho 59-24879, a liquid type ECD using organic molecule type viologen molecule derivatives that reversibly form states of coloration/color extinction as the electrochromic material (EC material) has been known. However, ECDs using the viologen molecule derivatives involve a problem that response speed or degree of light shielding is insufficient. In addition, as a light amount control device, it is necessary that the light transmissivity can be controlled in a visible light region (wavelength at 400 to 700 nm), and no sufficient characteristics can be obtained with the ECD material as described above.
The present inventors have noted on a light control device utilizing deposition/dissolution of a metal salt, instead of ECD, and have found that it can provide more excellent characteristics than the EC material with respect to the response speed and the degree of light shielding.
While various metal salts can be used for such an optical device, those systems using, particularly, deposition/dissolution of silver particles are excellent in view of optical characteristics. That is, an electrolyte is used as the material for a reversible plating, that is, RED (Reversible Electro-Deposition) in which a solution for the electrolyte shows no absorption spectrum in a visible light region (wavelength at 400 to 700 nm) upon preparation and causes deposition/solution of silver particles from a silver salt (including silver complex salt) of forming substantial uniform light shielding in the visible light region upon coloration. Further, the silver salt has a possibility of deposition/solution also by control for driving. Meanwhile, a cyan type solution has been used so far as a plating bath regarding deposition of silver particles from a silver salt but, since the cyan type solution is fatally poisonous, it is preferred to use a non-cyan type silver salt in the optical device of the present invention in view of safety for operation environment and discarding of liquid wastes.
Under the situations described above, it is possible to provide a non-light emitting type optical device such as an optical filter which consumes less electric power and which is suitable to a visible light region by the use of a reversible system of depositing/dissolving a metal from a metal salt on a transparent electrode of an optical device, that is, by the use of an RED material as a reversible plating material.
FIGS. 1A and 1B and FIG. 2 show a cell structure of an existent electrochemical light control device described above.
As shown in FIG. 1A and FIG. 2, a pair of transparent glass substrates 4 and 5 are disposed at a predetermined distance as a display window. As shown in FIG. 1A, working electrodes 2 and 3 each comprising an indium tin oxide (ITO) film obtained by doping tin to indium oxide are opposed to each other on the inner surfaces of the substrates 4 and 5, respectively, and an electrolyte 1 containing a metal salt is sealed between the opposed working electrodes 2 and 3. Counter electrodes 6 are disposed at the circumferential edges between the substrates 4 and 5 and function also as spacers, by which the sealed electrolyte 1 is sealed between the substrates 4 and 5.
In the optical device described above, when a DC driving voltage is applied for a predetermined period of time, as shown in FIG. 1B, between the counter electrode 7 as the positive electrode and the working electrodes 2 and 3 as the negative electrode, metal ions contained in the electrolyte take place the oxidation/reduction reaction at the negative electrode as shown by the following formula (1):
Mn++nexe2x88x92xe2x86x92Mxe2x80x83xe2x80x83(1) (n: natural number) 
and the working electrodes 2 and 3, which function as the negative electrode, change from transparent to colored states by deposited metal particles. FIG. 1B is a conceptional view illustrating the electrochemical mechanism in this reaction.
When the foregoing process is explained specifically to a case of using a silver salt solution as the electrolyte 1, a silver plate is used for the counter electrodes 7 and the silver salt solution is formed, for example, by dissolving silver bromide into dimethylsulfoxide (DMSO). As shown in FIG. 1B when a DC driving voltage is applied for a predetermined period of time between the counter electrode 7 as the positive electrode and the working electrodes 2 and 3 as the negative electrode, oxidation/reduction reaction is taken place for silver ions at the negative electrode as shown by the following equation (2):
Ag+exe2x88x92xe2x86x92Agxe2x80x83xe2x80x83(2) 
and the working electrodes 2 and 3, which function as the negative electrode change from transparent to colored states by deposited Ag particles.
When the metal particles are deposited on the working electrodes 2 and 3 as described above, a specified reflection color with the deposited metal particles is observed through the display window. The filter effect due to the coloration, namely, the transmissivity for the visible light (or density of coloration) changes depending on the level of voltage or the application time thereof. Accordingly, the cell can function as a variable transmissivity display device or an optical filter by controlling the factors.
On the other hand, in a state where the cell is in the colored state, when a DC voltage is applied in the opposite direction between the counter electrode 7 and the working electrodes 2 and 3, the working electrodes 2 and 3 on which the metal particles are deposited now act as the positive electrode to take place a reaction of the following formula (3):
Mxe2x86x92Mn++nexe2x88x92xe2x80x83xe2x80x83(3) 
and the metal particles deposited on the working electrodes 2 and 3 are restored from the colored state to the transparent state.
This is to be explained again to a case of using a silver salt solution for the electrolyte 1. When a DC voltage is applied in the direction opposite to the above between the counter electrode 7 and the working electrodes 2 and 3 in a state where the cell is in the colored state, the working electrodes 2 and 3 on which Ag particles are deposited now act as the positive electrode to take place the reaction of the following formula (4):
Agxe2x86x92Ag++exe2x88x92(4) 
and Ag particles deposited on the working electrodes 2 and 3 are restored from the colored state to the transparent state.
FIG. 3 and FIG. 4 show another electrochemical light control device of the related art.
In this example, as shown in the cross sectional view of FIG. 3, working electrodes 8a, 8b, 8c, 8d, 8e and 9a, 9b, 9c, 9d, 9e each comprising a pair of ITO films are opposed to each other on the inner surfaces of a pair of transparent glass substrates 11 and 12 constituting a cell. Counter electrodes 7a, 7b each comprising a silver plate are disposed to the outer circumference of the outer working electrodes 8e and 9e. The substrates 11 and 12 are kept and sealed at a predetermined distance by a spacer 13 and an electrolyte 1 is sealed between them.
As shown in a plan view of FIG. 4, the working electrodes 8a-8e and 9a-9e, and the counter electrodes 7a and 7b are planer electrodes formed in a concentric pattern. Each of the electrodes paired as 8a with 9a, 8b with 9b, 8c with 9c, 8d with 9d, 8e with 9e and 7a with 7b, respectively, are connected to driving power sources 14a, 14b, 14c, 14d, 14e and 14f by way of wirings 15a, 15b, 15c, 15d, 15e and 15f, respectively, each comprising fine chromium wires.
In this constitution, metal particles can be deposited from the electrolyte 1 on each of the electrodes as the negative electrode and colored by applying a predetermined potential (V1, V2, V3, V4 and V5, V6 being a standard potential relative to the counter electrodes 7a and 7b) to each of the opposing pair of working electrodes 8a and 9a, 8b and 9b, 8c and 9c, 8d and 9d, 8e and 9e respectively. The filter effect by the coloration, namely, the transmissivity for the visible light (or density of coloration) changes with the level of the voltage or the application time thereof.
If V1=V2=V3=V4=V5, the cell can be colored uniformly over the entire region and the degree of density can be changed uniformly in accordance with the voltage or the application time thereof. Further, if it is defined as |V1| greater than |V2| greater than |V3 greater than |V4| greater than |V5|, the color density decreases from the central portion to the periphery (that is, transmissivity is increased). On the other hand, if it is defined as |V1| less than |V2| less than |V3| less than |V4| less than |V5|, the transmissivity is decreased from the central portion to the periphery. The constitution is useful as an optical diaphragm for use in CCD (Charge Coupled Device) such as of a television camera and since the size of the device can be reduced, it can sufficiently cope with increase for the integration degree of CCD.
Then, the problems in the existent electrochemical light control devices described above are to be explained.
(1) Effect of Reaction of the Residue of Deposited Metal and Light Shielding Material on the Working Electrode
In the existent electrochemical light control devices, a black resist of a black color is often coated to shield light to a portion other than the effective region for controlling light effectively at the portion of the working electrode.
That is, after forming working electrodes, counter electrodes and, if necessary, reference electrodes on a substrate such as of glass by the same fabrication method as in semiconductor manufacturing processes, a light sensitive black resist is coated by spin coating or like other means, and conducting exposure and development using a mask having a predetermined pattern for peeling the portion for the working electrode, the counter electrode and the reference electrode to obtain a desired pattern in which the black resist of the electrode portion is peeled.
When an electrolyte prepared by dissolving a silver salt to a mixed solution of DMSO/AN (dimethylsulfoxide/acetonitrile) is used for example, a resist material mainly comprising propylene glycol monomethyl ether is used such that the black resist is not dissolved in the electrolyte. In the black resist, light shielding die or a pigment is generally incorporated in the matrix material as described above to obtain a desired light shielding property.
However, after the step as described above, when deposition/dissolution of a metal is repeated on the working electrode, uneven deposition occurs to the electrolyzed metal on the working electrode or the electrolyte metal on the surface is not dissolved completely (undissolved deposit) even if the electrode is sufficiently polarized to the oxidation state, probably because of the effect of the black resist residue remaining on the surface of the working electrode.
In such a situation, the light shielding is not sufficient or the brightness of a picture element cannot be ensured sufficiently upon transparent state to deteriorate the device characteristics.
Further, the counter electrode and/or the reference electrode (third electrode) disposed for monitoring/controlling the potential of the working electrode and/or the counter electrode may sometimes be constituted with a material more noble than the material of a metal contained in the electrolyte (lower ionization tendency). For example, in a case of using an electrolyte containing silver, the counter electrode and/or the reference electrode is sometimes constituted with platinum, palladium or gold which is more noble than silver. This is because it is stable in the electrolyte and the metal (silver) can be deposited/dissolved smoothly on the electrode, particularly, in a case of the counter electrode.
In such a case, portions other than the counter electrode and/or the reference electrode are previously covered with a photoresist and platinum or the like is formed by a gas phase growing method such as a physical vapor deposition method. In this case, the melting point, particularly, of platinum is as high as 1769xc2x0 C. and the temperature in the vapor deposition vessel rises to 200xc2x0 C. or higher by which the resist is cured and the resist is sometimes cracked by the heat. Accordingly, in the subsequent lift-off operation, the resist may remain as the residue, particularly, on the working electrode or particles of platinum intruding through the cracked portion of the resist may be adhered on the surface of the working electrode not removably. In such a situation, when the optical device having the optical element is driven, undesired effects are also given on the optical characteristics of the element such as electrodeposited material remains undissolved on the working electrode.
Further, when the optical device is driven and, particularly, the deposition material is deposited/dissolved, particularly, on the working electrode, if a high overvoltage is applied to the working electrode, a considerably high voltage is applied to the black resist between the lead electrode for the working electrode and the electrolyte to cause bubbles by deposition of the black resist. Therefore, the insulation withstand voltage is lowered, which further induces bubbling and reaction between lead electrode and the electrolyte. In this case, stable operation of the optical device is no more possible.
As described above, in a case where the portions of each of the electrodes other than the effective region are shielded with a light shielding material such as a black resist in the electrochemical optical element, disadvantages may sometimes occur at the lead electrode portion. In addition, when the electrochemical optical element is fabricated, the photoresist used for fabrication or the portion of the black resist to be removed may not sometimes be removed completely to leave residues and bring about a disadvantage such as undissolved electrodeposition film.
(2) Specific Light Absorption of the Electrodeposited Film on the Working Electrode
In the existent electrochemical light control element described above, tin-doped indium oxide is used for the working electrode. In this case, the electrodeposited film sometimes exhibits a specific light absorption. For example, most of commercially available ITO has In/Sn element ratio (or ratio for the number of atoms) of about 4(8:2) to 9(9:1). When such material is used for the working electrode and a silver film is deposited on the working electrode at a room temperature, the silver film shows light absorption at 500 to 600 nm and is colored red. A disadvantage is caused in such a situation that the photographed image upon light control is pigmented to the color of the deposition film.
(3) Overpotential at Working Electrode
High resistance of the working electrode causes deviation of the potential at the electrode from an equilibrium potential (that is polarization) upon driving the device.
Then, when the working electrode is overpotential, various side reactions, such as a decomposition of the electrolyte, may occur. Particularly, in using an electrolyte which contains a silver salt and an iodic salt as a supporting salt, yellowing of the electrolyte is observed perhaps because the iodic ions are oxidized into molecules.
(4) Life of the Counter Electrode
In the existent electrochemical light control devices, the counter electrodes 6, 7a and 7b consisted of the same kind of material as the metal contained in the electrolyte 1. For example, when a pure silver metal plate is used as it is in a case where the electrolyte 1 comprises a silver salt solution, smooth electrochemical reaction can be conducted mainly for silver on the counter electrode. However, there is a problem that the cost for the material of the counter electrode increases. Further, as the life of the optical element increases, inactivated metal particles deposited on the counter electrode diffuse and suspend in the electrolyte to contaminate the inside of the element and which may lead to a problem of lowering the transmissivity in the transparent state of the element or causing short-circuit between the electrodes.
For example, in the device shown in FIG. 3 and FIG. 4, upon color extinction of the working electrode, material mainly containing a metal is deposited on the counter electrodes 7a and 7b as the negative electrode. In this case, since lines of electric force of the electric field are concentrated to the angled portion of the electrode as shown in FIG. 5 (illustrated as 7b in the drawing), the material is grown on the portion into relatively large particles and deposited. Different from thin-film deposition material B at other portions, the particulate deposition material A is not easily dissolved upon coloration of the working electrode and, as shown in the figure, detached in an inactivated particulate state as it is and dispersed and suspended in the electrolyte 1. When such deposition material of inactivated particles is increased in the electrolyte, it lowers the transparency of the device upon color extinction of the working electrode and such particles also cause short-circuit between the electrodes.
In view of the above, the present inventors have studied, as a countermeasure, a method of forming a layer containing at least one kind of conductive particles such as carbon material on a current collector instead of using, for example, a metal plate such as a pure metal plate as it is for the material of the counter electrode and have proposed an optical device, for example, an electrochemical light control device, as well as a fabrication method thereof as Japanese Patent Application Hei 10-9458 (filed on Jan. 21, 1998 in Japan).
However, while the counter electrode can be constituted with a relatively inexpensive material and it has an excellent performance that particles of inactivated deposition material are less formed on the counter electrode according to the patent application (hereinafter referred to as a prior application), it has been found to still have a room for an improvement.
That is, when the carbon material is used as the counter electrode, when the device is driven and dissolution/deposition reaction is repeated a number of cycles at the transparent electrode and the counter electrode, adhesion between the current collector as the underlying electrode and the carbon material is lowered to sometimes detach the layer of the carbon material from the current collector. The current collector means herein an underlying electrode that supplies charges to the carbon material but the underlying electrode itself does not electrochemically react with the electrolyte because it is covered with the carbon material.
When the conductive particle layer is detached, the current collector is in direct contact with the electrolyte not by way of the layer of the carbon material and has a direct concern to the reaction with the electrolyte. In such a case, interface polarization between the current collector and the electrolyte increases remarkably in an underlying electrode material that transfer of charges from the current collector to the electrolyte is not taken place smoothly.
Further, in a case of the current collector consisting of a material that can transfer charges to the electrolyte relatively smoothly, deposition of a metal or a compound containing the metal on the current collector, or side reaction such as decomposition of the electrolyte component may take place. If the deposition material has a particularly insulative property, subsequent charge transfer is not conducted smoothly and, as a result, polarization increases extremely. Such a great polarization requires large power consumption and, in addition, promotes side reactions thereby resulting in a problem such as shortening of the device life.
(5) Temperature Dependence of the Transmissivity Control
In the existent electrochemical optical device, the deposition form of the deposition material on the working electrode differs depending on the working temperature and, particularly, the deposition rate of the deposition material containing a metal tends to be affected by temperature. That is, the deposition rate is faster at a higher temperature than at a lower temperature, and the thickness of the deposition film is larger as a temperature is higher at an identical current density even within an identical time.
In the optical device described above, since the degree of light screening is changed by the thickness of the deposition film, the desired light shielding degree to be obtained depends on the temperature, current density and deposition time. When comparison is made at an identical deposition time, it has been a problem that the light shielding degree of the optical device greatly is affected by temperature and current density and is hard to operate stably.
(6) Change of Transmissivity
In the existent electrochemical optical device, when a deposition material containing a metal such as silver is deposited (electrodeposition) on the surface of the working electrode and then left as it is while short circuiting the external circuit, since the electrodeposited material is dissolved again into the electrolyte to reduce the thickness of the deposition film, the transmissivity was increased. Further, even when the external circuit is opened as it is after depositing the film (electrodeposition), the electrodeposited material is also dissolved again in the electrolyte although the dissolution rate is somewhat slower to gradually increase the transmissivity. If such phenomenon should occur, no stable light control can be attained, for example, in a CCD camera to bring about a disadvantage that the image is blurred.
(7) Peeling of Electrodeposition Film on the Working Electrode
In the existent electrochemical light control device described above, deposition material contained in the electrolyte is electrodeposited on the surface of a working electrode comprising ITO if the amount of electric current supplied to the electrode is increased and the thickness of the deposition film increases, the deposited film is sometimes peeled from the surface of the working electrode perhaps because of the increase in the stresses caused to the deposition film. This film peeling was remarkable, particularly, in a case where the transparent conductive film constituting the working electrode has a layer of tin oxide formed on tin oxide or ITO.
If such film peeling should occur, the peeling portion can no more shield the light and light shielding is decreased as a whole and, depending on the case, no sufficient light sealing can be attained in a CCD camera and brings about a problem of disadvantage such as blurred images.
Further, if such peeling of deposition film should occur, when the working electrode is polarized to the oxidation state to dissolve the electrodeposition material, it sometimes results in undissolved deposit, since current cannot be supplied sufficiently over the entire film.
(8) Limit for the Size Reduction of Mechanical Diaphragm
On the other hand, for the light amount control of CCD (charge Coupled Device) cameras, mechanical diaphragm for controlling the amount of light has been used so far. However, along with the reduction of the size in CCD cameras, as the range for the diaphragm is decreased, the peripheral machinery constitution for driving the same is rather enlarged in the scale in the existent mechanical diaphragm, which imposes a limit as the reduction of the size for the entire system. Further, as the size of CCD is getting smaller, various problems have occurred such as blurred images under the effect of light diffraction in the mechanical diaphragm described above.
In view of the above, it may be considered as a means for the diaphragm in a camera system to cope with problems for the size reduction as the entire system and of blurred images by controlling the light amount using the electrochemically light control device. However, the existent electrochemical light control device described above involves the problems of specific light absorption of the electrodeposition material and undissolved deposit of the electrodeposition material to lower the light shielding and increase the transmissivity, which forms a bar in a case of using the electrochemical optical device to the camera system.
The present invention has been accomplished in view of the foregoing various situations described above and a first object of the present invention is to provide an electrochemical light control device utilizing deposition/dissolution reaction of a material mainly containing a metal, which is free from problems due to the presence of a light shielding material in a case having a shielding structure with the light shielding material such as a black resist, enables stable operation and can attain a long life of the device.
Further, it is an object thereof to provide a fabrication method capable of obtaining a highly reliable electrochemical optical device without causing disadvantages such as undissolved deposit of the electrodeposition material caused by the residue of the photoresist used for fabrication, or the residue of the material such as the black resist.
Further, it is an object of the present invention to provide a camera system capable of reducing the size and overcoming the problem of blurred images or the like, by solving the problems in the existent electrochemical light control element such as undissolved electrodeposition materials as described above thereby suppressing peeling of the film deposited on the working electrode and suppressing lowering of the light shielding and increase in the transmissivity to enable application to the camera system.
An electrochemical optical element according to the present invention has at least a transparent electrode as a working electrode and a counter electrode and an electrolyte disposed in contact with the working electrode and the counter electrode in which light is controlled electrochemically by controlling an electric field applied to the electrolyte, wherein an insulation film is formed on a lead electrode for at least one of electrodes.
According to the present invention, since the insulation film is formed on the lead electrode, the black resist or the like is formed by way of this insulation film over the lead electrode. Accordingly, a problem caused by the contact of the lead electrode with the black resist or the like, can be overcome. Such an insulation film is formed on at least one of the lead electrodes, and the insulation film is present between the lead electrode and the black resist, so that even when a high overvoltage is applied to the lead electrode, it is applied mainly along the insulation film, so that with the black resist or the like, does not take place an electrochemical reaction by the over voltage and, accordingly, high reliability and long life of the optical element can be obtained.
A fabrication method for an electrochemical optical element according to the present invention resides in a fabrication method for an optical element having at least a transparent electrode as a working electrode and a counter electrode and an electrolyte disposed in contact with the working electrode and the counter electrode in which light is controlled electrochemically by controlling an electric field applied to the electrolyte, wherein at least a portion including the transparent electrode as the working electrode is covered with an insulation film before at least one resist step.
According to the present invention, since at least the portion including the transparent electrode is covered with the insulation film, if any residue of the resist or the like remains on the portion in the subsequent resist step, disadvantage caused to the electrode can be prevented. Particularly, when the insulation film is previously formed on the surface of one of the electrodes in which a deposition material containing a metal is electrodeposited/dissolved, since the light shielding material such as a black resist is not in direct contact with the electrode, disadvantage given to the black resist or the like on the electrode can be prevented. Even if any residue such as of the black resist should remain undesired effects can be suppressed. Subsequently, when the insulation film is removed by the etching or like other means after exposure/development of the black resist, residue of the black resist or the like does not remain on the surface of the electrode and an electrode with no undissolved electrodeposition material can be obtained.
Further, the present invention can overcome also the problem caused by the photoresist used generally for light shielding, in addition to the black resist used generally for patterning. That is, since also the photoresist for the patterning is not in direct contact with the surface of the electrode covered with the insulation film, even if the photoresist is cured and suffers from cracking and vapor deposition products intrude through the cracks in a case where the film of a high melting metal or the like is formed subsequently by way of a gas phase growing method such as physical vapor deposition on other electrodes, residue of such as photoresist does not remain on the surface of the electrode on which the material containing a metal such as silver is deposited thereafter if the insulation film is removed by etching or like other method to obtain an electrode with no undissolved electrodeposition material in the electrolyte.
Further, in a camera system according to the present invention, an electro-optical element having an insulation film formed on the lead electrode for at least one of the electrodes is disposed for controlling the amount of light in an optical path (hereinafter also referred to as a camera system according to the present invention).
According to the present invention, since an optical device having the insulation film formed on the lead electrode for one of the electrodes is used, no undissolved electrodeposition material is formed as described above.
Further, the optical device has an electrode with no decomposition or damage of the light shielding layer such as the black resist and a camera system capable of reducing the size and overcoming the problem such as blurred images can be provided by disposing such an electro-optical element for controlling the amount of light in an optical path.
The camera system according to the present invention can be practiced as an embodiment in which various forms of the electrochemical light control elements according to the present invention described above, are disposed in an optical path for controlling the amount of light.
According to the camera system of the present invention as described above, since the electrochemical optical element capable of controlling the amount of light by the application of an electric field is applied as the optical diaphragm in a CCD camera or the like, it requires no mechanical constitution of a large scale different from existent mechanical diaphragm and, accordingly, it is possible to reduce the size, that is, to a substantially effective range of the optical path, and diffraction can be prevented by controlling the amount of light by the level of the applied electric field, which is thereby capable of effectively preventing blurred images.
A second object of the present invention is to provide an optical device having a working electrode of a relatively reduced resistance and excellent spectral characteristics, and a fabrication method thereof, as well as a camera system capable of attaining the reduction of the scale of the system and preventing blurred images by using the optical device for controlling the amount of light.
That is, the present invention provides an optical device having an electrode formed of an oxide layer in which indium is doped to tin, wherein indium/tin is 1.5 or less by the element ratio (or ratio for the number of atoms) (hereinafter referred to as an optical device of the present invention).
According to the optical device of the present invention, since the oxide layer formed by doping tin to indium so as to be within an appropriate range for the indium/tin element ratio of 1.5 or less as described above (preferably, from 1.5 to 0.5) is used for the electrode, when it is used, for example, as the working electrode, spectral characteristics can be improved, for example, suppression for the coloration of the electrodeposited film and the resistance of the oxide electrode can be decreased.
Further, the present invention also concerns a fabrication method for an optical device having an electrode formed of an oxide layer in which indium is doped to tin (in which indium/tin is 1.5 or less by the element ratio), wherein the oxide layer is formed by a gas phase film forming method (hereinafter referred to as a fabrication method of the present invention).
According to the fabrication method of the present invention, since the oxide layer can be formed to a desired film quality and thickness by changing the target or the discharging condition in one identical vacuum apparatus, for example, by a sputtering or vapor deposition method as the gas phase film forming method, it is possible to provide a fabrication method for an optical device of favorable reproducibility that can provide the same effect as described above.
Further, the present invention concerns a camera system having an optical device disposed in an optical path for controlling the amount of light, the device having an electrode formed of an oxide layer in which indium is doped to tin where indium/tin is 1.5 or less by the element ratio.
According to the camera system of the present invention, since the optical device incorporated therein is excellent in the spectral characteristic and capable of controlling the amount of light by the application of the electric field to the electrolyte, no large scale mechanical constitution is required different from existent mechanical diaphragm and the size can be reduced substantially to an effective range of an optical path, and the amount of light can be controlled by the level of the applied electric field to prevent diffraction and also effectively prevent blurred images.
Further, the present invention concerns an optical device having an electrode, particularly a transparent electrode, formed of a laminate comprising an oxide layer in which indium is doped to tin and a tin oxide layer (hereinafter referred to as an optical device of the present invention).
According to the optical device of the present invention, since the electrode is formed of a laminate comprising an oxide layer in which tin is doped to indium and a tin oxide layer, the spectral characteristics of an electrodeposited film containing a metal, when deposited on the electrode, can be improved by the tin oxide layer and, further, the resistance as the entire electrode can be decreased by reducing the thickness of the oxide layer (for example, to 130 nm or less). As a result, it is possible to suppress polarization of the electrode upon driving of the device.
Further, the present invention provides a fabrication method for the optical device having an electrode formed of a laminate comprising an oxide layer in which tin is doped to indium and a tin oxide layer wherein the tin-doped indium and/or tin oxide layer is formed by a gas phase film forming method (hereinafter referred to as a fabrication method of the present invention).
According to the fabrication method of the present invention, since the tin oxide layer can be formed contiguous with the oxide layer and the tin oxide layer can be formed to a desired film quality and thickness by changing the target or the discharging condition in one identical vacuum apparatus, for example, by a sputtering or vapor deposition method as the gas phase film forming method, it is possible to provide a fabrication method for an optical device of favorable reproducibility that can provide the same effect as described above.
Further, the present invention concerns a camera system in which an optical device is disposed in an optical path for controlling the amount of light, the device having an electrode formed of a laminate comprising an oxide layer in which tin is doped to indium and a tin oxide layer (hereinafter referred to as a camera system of the present invention).
According to the camera system of the present invention, since the optical device incorporated therein is excellent in the spectral characteristic and capable of controlling the amount of light by the application of the electric field to the electrolyte, no large scale mechanical constitution is required different from existent mechanical diaphragms and the size can be reduced substantially to an effective range of the optical path, and the amount of light can be controlled by the level of the applied electric field to prevent diffraction and also effectively prevent blurred images.
A third object of the present invention is to provide an optical device in which adhesion of a layer comprising conductive particles such as a carbon material is improved in the counter electrode to prevent peeling of the layer described above and the potential of the counter electrode is stabilized to enable stable driving and which can lower the electric power consumption and make the device life longer, and a fabrication method thereof.
A further object of the present invention is to provide an optical device such as an electrochemical light control element in which the counter electrode of the electrochemical optical device utilizing deposition/dissolution reactions of materials such as metals can be constituted with a relatively inexpensive material and particulate deposits such as of an inactivated metal are less formed on the counter electrode, as well as the fabrication method thereof.
That is, the present invention concerns an optical device comprising a working electrode, a counter electrode and an electrolyte disposed in contact with both of the electrodes, and light is electrochemically controlled by an electric field applied to the electrolyte, wherein the counter electrode comprises a first layer comprising conductive particles, a second layer comprising a polymeric layer and a third layer comprising a current collector, and the second layer is formed between the first layer and the third layer (hereinafter referred to as the optical device of the present invention).
According to the optical device of the present invention, the polymeric layer as the second layer can bond the first layer comprising the conductive particles and the third layer comprising the underlying current collector to improve the adhesion. As a result, since this can stabilize the potential of the counter electrode and can delay occurrence of peeling between the first layer comprising the conductive particles and the third layer comprising the underlying current collector and accompanying increase of the polarization, it is possible to suppress increase of the consumption power and side reaction with the electrolyte for a long period of time to make the life of the optical device longer.
Further, since the first layer comprises the conductive particles, when a mixture comprising them in admixture with a binder is printed or coated to form the first layer, it can be easily set to a predetermined shape and the counter electrode can be formed to a shape with no substantially angle corner, so that localized concentration of electric field on the counter electrode can be moderated and deposition of inactivated particles including metal on the counter electrode can be suppressed or prevented. As a result, it is possible to prevent the particles of inactivated deposition material from diffusing or suspending in the electrolyte to lower the transparency of the element, or from short-circuiting the electrodes.
Further, the present invention provides a fabrication method for an optical device having a working electrode and a counter electrode and an electrolyte disposed in contact with both of the electrodes and light is controlled electrochemically by an electric field applied to the electrolyte, wherein the method comprises forming a second layer comprising a polymeric layer on a third layer comprising a current collector by a electrochemical polymerizing process, and forming a first layer comprising conductive particles on the second layer (hereinafter referred to as a fabrication method of the present invention).
According to the fabrication method of the present invention, since the second layer, in particular, of the optical device according to the present invention is formed by the electrochemical polymerization method, a dense and homogeneous polymeric layer can be formed and since the first layer is formed as a coating layer or the like comprising the conductive particles, the optical device according to the present invention having the foregoing function and effect can be fabricated with favorable reproducibility.
Further, the present invention concerns a camera system in which an optical device is disposed in an optical path for controlling the amount of light, wherein the device has a counter electrode comprising a first layer including conductive particles, a second layer comprising a polymeric layer and a third layer comprising a current collector, and the second layer is formed between the first layer and the third layer (hereafter referred to as a camera system of the present invention).
According to the camera system of the present invention, since the optical device incorporated therein is excellent described above, it is possible to suppress increase of the consumption power and make the life of the camera system longer. And since no large-scale mechanical constitution is required different from existent mechanical diaphragms, the size can be reduced substantially to an effective range of the optical path. Further, the amount of light can be controlled by the level of the applied electric field to prevent diffraction and also effectively prevent blurred images.
Further, a fourth object of the present invention is to provide, in an electrochemical optical device utilizing deposition/dissolution of a material including a metal for controlling light, an optical device capable of obtaining a stable light shielding degree, a driving method thereof, as well as a camera system capable of reducing the size of the system and preventing blurred images by applying the optical device for controlling the amount of light.
That is, the optical device according to the present invention have a working electrode, a counter electrode and an electrolyte disposed in contact with both of the electrodes and light is controlled electrochemically by an electric field applied to the electrolyte, wherein the optical device further comprises a control device or unit for controlling a driving current in accordance with a temperature of the electrolyte in the optical device.
Further, the driving method according to the present invention comprises controlling the driving current in accordance with the temperature of the electrolyte in the optical device.
Further, a camera system according to the present invention has the optical device as described above disposed in an optical path for controlling the amount of light.
According to the optical device and the driving method of the present invention, since the driving current is controlled in accordance with the temperature of the electrolyte in the optical device for electrochemically controlling the light, an averaged transmissivity, that is, a stable degree of light shielding can be attained irrespective of the temperature of the electrolyte.
Further, a fifth object of the present invention is to provide, in an electrochemical optical device utilizing deposition/dissolution of a material such as a metal for controlling light, an optical device improved so as to effectively suppress increase of the transmissivity (or decrease of the reflectivity) caused by electrodeposition of a deposition material containing a metal and subsequent dissolution of the electrodeposited material into the electrolyte again and prevent disadvantage such as blurred images, a driving method thereof, as well as a camera system capable of reducing the size of the system and preventing blurred images by using the optical device for controlling the amount of light.
That is, the optical device according to the present invention comprises a working electrode, a counter electrode and an electrolyte disposed in contact with both of the electrodes in which light is controlled electrochemically, wherein a current supply means is disposed for supplementing a dissolved portion of a predetermined electrodeposited material after electrodeposition of the material to the working electrode.
Further, the driving method according to the present invention for an optical device having a working electrode, a counter electrode and an electrolyte disposed in contact with both of the electrodes, wherein light is controlled electrochemically, comprises the steps of electrodepositing a material on the working electrode and then supplying an electric current for supplementing a dissolved portion of the electrodeposition material.
Further, according to the camera system of the present invention, the optical device is disposed in the optical path for controlling the amount of light.
According to the optical device of the present invention and the driving method thereof, in the driving device for electrochemically controlling the light, since a material containing the predetermined material, for example, a material containing silver is electrodeposited on the working electrode and then an electric current is supplied for supplementing the dissolved portion of the electrodeposition material, so that reduction for the thickness of the electrodeposited film due to spontaneous dissolution into the electrolyte and an accompanying change of the optical characteristics such as light transmissivity can be suppressed effectively and, as a result, sufficient light shielding can be attained, for example, in a CCD camera.
Further, according to the camera system of the present invention, since the optical device attached thereto can control the amount of light electrochemically by the application of the electric field to the electrolyte, no large scaled mechanical constitution is required different from existent mechanical diaphragms and it can be reduced to a size for the substantially effective range of the optical path, and the amount of light is controlled by the level of the applied electric field to prevent diffraction and also effectively prevent blurred images.
Further, a sixth object of the present invention is to provide an electrochemical optical device utilizing deposition/dissolution of a material including a metal for light control, in which an optical device capable of suppressing the deposited film of the material from peeling from the working electrode, suppressing lowering of the light shielding and increase of the transmissivity, without causing disadvantage such as blurred images in a cCD camera and not resulting in undissolved electrodeposition material, and a driving method thereof, as well as, a camera system capable of reducing the size and with no blurred images.
That is, the present invention provide an optical device having a working electrode, a counter electrode and an electrolyte disposed in contact with both of the electrodes and light is electrochemically controlled by an electric field applied to the electrolyte, wherein the optical device comprises means for polarizing the working electrode in the direction of oxidation before electrodeposition of a material containing a metal on the working electrode (hereinafter referred to as an optical device of the present invention).
According to the optical device of the present invention, since the electrodeposition is conducted after polarization of the working electrode to the oxidation direction, the state of the surface of the working electrode is stabilized so as to be easily electrodeposited and, subsequently, the material containing a metal is electrodeposited on the working electrode from the electrolyte, so that peeling of the electrodeposited film can be prevented. As a result, an optical device of excellent characteristics with suppressed lowering of the light shielding and increase of the transmissivity can be attained and it is possible to provide an optical filter not causing blurred images and undissolved electrodeposition material also when it is applied to a CCD camera or the like.
Further, the present invention concerns a driving method of an optical device having a working electrode, a counter electrode and an electrolyte disposed in contact with both of the electrodes in which light is controlled electrochemically by an electric field applied to the electrolyte, wherein the working electrode is polarized in the oxidation direction by a polarization means before electrodepositing the material including a metal on the working electrode from the electrolyte (hereinafter referred to as a driving method of the present invention).
According to the driving method of the present invention, since the working electrode is previously polarized to the oxidation direction before electrodeposition of the material on the working electrode, the surface state of the working electrode can be stabilized to provide the same effect as that for the optical device according to the present invention described above.
Further, the present invention also provides a camera system (hereinafter referred to as a camera system of the present invention) in which the optical device according to the present invention is disposed for controlling the amount of light in an optical path.
According to the camera system of the present invention, since the optical device capable of controlling the amount of light by the application of the electric field to the electrolyte is used for the diaphragm such as of a CCD camera, no large scale mechanical constitution is required different from the existent mechanical diaphragm and the size can be reduced to substantially an effective range of optical path, and the amount of light can be controlled by the level of the applied electric field to prevent diffraction and also effectively prevent blurred images.
Referring to the transparency in the present invention, the transmissivity of the working electrodes is generally 70% or more in a visible light region (or aimed intended wavelength region). Further, the optical device comprises a transparent electrode as the working electrode and have a counter electrode paired with the working electrode in the present invention. It may have a structure further comprising an appropriate reference electrode.